Nonlinear optics describes the behavior of light in nonlinear media, that is, media in which the dielectric polarization responds nonlinearly to the electric field of the light, and the light can be exemplified by high-power laser. Weakly bonded valence electrons are polarized by the electric field, whereas the extent of polarization depends on the polarization of the molecules of the media and leads to a change in the distribution of the electric field of the ions of the media. Given the change in the distribution of the electric field of the ions of the media, dipole moment no longer linearly correlates with a light wave field, thereby resulting in a change in the phase, frequency and amplitude of light. The magnitude of the change is a function of incidence strength. Important components, such as those for use in processing, say regulating, turning on, turning off and storing, light-related information, are manufactured from materials with different nonlinear optical effects. The commonest conventional optoelectronic phase modulation device is designed according to the electro-optic (EO) effect of a second-order nonlinear optical material. Light controlling devices operating by the nonlinear optical effect include light modulation components and light switches. EO effect-based materials are capable of second harmonic generation (SHG) effectuated in a second order nonlinear manner and thereby exhibit first order electro-optic effect characterized by first-power proportional variations of the refractive index in accordance with the electric field. To meet the application requirement of nonlinear optical materials, an optical material must not only compulsorily exhibit a satisfactory nonlinear optical effect in a fixed direction and thereafter become fixed in place but also exhibit satisfactory high temperature stability.
Both Taiwan patent 200700461 and Taiwan patent 200700462 disclose novel chromophores derived from benzobisthiazole and polyimide which exhibits satisfactory thermal stability and disclose combining the two to achieve thermal stability and second order nonlinear optical characteristics. Although poly(benzobisthiazole) (PBT) exhibits satisfactory second order nonlinear optical characteristics, it cannot be completely dissolved in conventional organic solvents, thereby being limited in its application. To effectively enhance its solubility and maintain its good nonlinear optical characteristics, polyimide, which exhibits satisfactory solubility and processing properties, functions as a main chain. A chromophore derived from benzobisthiazole functions as a side chain which is grafted to the main chain of polyimide, so as to produce a polyimide which features thermal stability and second order nonlinear optical characteristics. Taiwan patent 085111870 provides a novel method of preparing a polymer film with second order nonlinear optical properties. The method is characterized in that molecules which have the nonlinear optical effect are doped by co-evaporation in the course of monomer vapor deposition and polymerization while undergoing polarization. One of the advantages of Taiwan patent 085111870 is that the film is manufactured in an extremely low polarization field and does not require any complicated polymerization process, thereby making it easy to manufacture numerous pieces of tailorable film of various types.
Taiwan patents 102127807 and 102112513 provide: a prepolymer for use in forming a nonlinear optical material which exhibits satisfactory nonlinear optical properties, thermal tolerance, insulation, compression tolerance, and transparency; a hardening material comprising the prepolymer; a composition comprising the hardening material and a solvent and adapted for use in coating; a nonlinear optical material formed by hardening the hardening material; and an optical waveguide using the nonlinear optical material and a light control device for use with the optical waveguide.
Directive hysteresis of an organic compound leads to a reduction in the nonlinear optical effect of the organic compound. This drawback is overcome by allowing an ion exchange reaction to take place between the organic compound and an organic intercalating agent, allowing admission and departure of monomers, and increasing an interlayer distance from 10 Å to 20˜30 Å. In an intercalation state, layers are neatly arranged, distributed and spaced apart by a fixed distance, with organic molecules sandwiched between layers to go against action forces exerted upon and between layers and prevent re-stacking. In an exfoliation state, layers are spaced apart by irregular distances and are irregularly aligned. The organic intercalating agent increases the distance between the layers and increases the affinity between an inorganic layer and an organic polymer; afterward, an organic/inorganic polymer nano-composite material is produced by polymerization, fluxing processing or a redistribution mechanism.
Related research papers, namely Macromol. Rapid Commun., 2008, 29,587-592., Polym. Adv. Technol., 2009, 20, 493-500, ACS Applied Materials & Interfaces, 2009, 1, 2371-2381, Polym. Chem., 2013, 4, 2747-2759, disclose: producing an organic-modified clay from a dendritic polymer ended with chromophores, allowing intercalation to occur to its unique functional group and montmorillonite (MMT), and blending them with polyimide to form a nano-composite material, wherein the dendritic structure binds the chromophores and intercalates with an ionic group of the MMT so as to disarrange them by exfoliation. The mixed material not only exhibits an optoelectronic effect characterized by central asymmetry achieved readily by self-assembly without undergoing polarization but also exhibits satisfactory thermal stability.
Jen and others put forth patents, such as US20120252995 A1, U.S. Pat. No. 8,173,045 B2, U.S. Pat. No. 7,425,643 B1, U.S. Pat. No. 7,390,857 B2, U.S. Pat. No. 8,409,713 B2, U.S. Pat. No. 8,648,332 B2 and U.S. Pat. No. 8,394,499 B2, to disclose structures which undergo crosslinking by Diels-Alder reactions to effectuate second order central asymmetry and chemical structural combinations for use in Diels-Alder reversible reactions, as described in U.S. Pat. No. 7,268,188 B2 and U.S. Pat. No. 7,144,960 B2, wherein the stability of the second order nonlinear optical material is enhanced as a result of crosslinking.